Project54 & UNH ECE bmcmahon on 25 Jun 2007 07:40 am
Rooftop Rain Event Logging Station
Datacasting is a technology Project54 is trying to take advantage of for communications between police headquarters and officers in the field. We’ve completed a field study on datacasting and have found that problems with signal reception sometimes happen during rain events. We’ve set up a Rooftop Rain Event Logging Station to further explore what is going on.
Three antennas were placed on the roof of Kingsbury to log statistics of the datacasting signal. In particular, we are interested in collecting signal-to-noise ratio and signal strength variations over time, especially during rain events. Here is what the antenna setup looks like:
The small omni-directional antennas mounted on aluminum ground planes simulate the receiver installation we installed on vehicles. This antenna is the most susceptible to signal degradation because it receives more multi-path interference, from many different directions, confusing our receiver. This is a picture of the receiver on the aluminum plane:
We also have two directional antennas that face opposite directions. The first, facing the NHPTV DTV transmitter, monitors the signal statistics for a base line. The second, facing away from the transmitter, measures the backscattered signal level, which has been shown to affect our omni-directional antenna. Here they are:
You can read more on our datacasting work in this paper. Two more papers will appear shortly and you will be able to find them here.
Benjamin McMahon
on 25 Jun 2007 at 7:55 am 1.andrewkun said …
You have two aluminum planes - why?
on 25 Jun 2007 at 9:17 am 2.bmcmahon said …
The second aluminum plate, not mentioned in the above article, also holds an omni-directional antenna, and was subsequently used to monitor additional signal statistics not available on our original signal monitor. The second omni-directional antenna is monitored with a Sencore AT1506 8-VSB signal analyzer loaned to us by NHPTV. These additional statistics give us more information from the demodulator such as EVM (error vector magnitude), multipath echo data, etc. The original signal monitor logs signal-to-noise ratio exclusively, and is the same receiver installed in the vehicles.